Application of laser in 3D object modeling and intelligent recognition

In the modern high-tech industry, components on unmanned production lines (Line for short), such as electronic components, electronic connectors, metal parts and non-metal parts, especially some radioactive or toxic components, usually need to be processed. On-line real-time dynamic recognition or detection, to determine its shape, state, and accuracy. The above functions can be easily realized by using laser and dynamic positioning technology.

The collection method of laser 3D information is to use laser irradiation to scan Line elements, and use more than two cameras with instantaneous dynamic positioning system. According to the characteristics of Line elements, the method of feature recognition mode is used to establish and compile intelligent recognition software, using the principle of fuzzy mathematics Compile data processing and modeling, edit intelligent teaching software, increase the number of cameras and laser scanners according to the complexity of the shape of the Line element, and finally realize the laser dynamic recognition of the shape and state of the Line element.

The principle of instantaneous dynamic positioning of Line components. Set the recognition area on the Line. When the component runs into the recognition area, an instruction is issued instantly. The laser starts to scan and collect the shape information of the component. The basic positioning feature data and size of the component are selected first, and the instant positioning is determined. “Line” or “surface”, the most effective selection method is to use the longest line of the outline of the Line element as the positioning line, and use the maximum area of ​​the outline of the Line element as the positioning surface, which is used as the positioning during the second instantaneous sampling The benchmark provides a precondition for the dynamic online collection and recognition of the three-dimensional shape and state of the component.

The mathematical model of the three-dimensional coordinate of the laser scanning object point effectively solves the problem of obtaining the three-dimensional information of the Line element. The application of the instantaneous dynamic positioning method better realizes the dynamic online collection and identification of Line components. The establishment of the feature recognition mode provides a new way for the visual recognition of the shape and state of Line components. It makes the recognition software easy to implement and become a practical application system.

Influence of process operating conditions

Etching is the key to the pattern decoration process of the metal plate mold. In order to obtain a pattern product with clear stripes and strong decorativeness, attention must be paid to controlling the conditions of the etching process. Mainly the temperature of the etching solution and the etching time. A slightly higher solution temperature can increase the rate of metal dissolution, that is, the rate of etching, and shorten the time required for etching. However, the etching solution is generally a strong acid solution. The strong acid solution is highly corrosive at high temperatures and is easy to protect The coating or corrosion-resistant ink softens or even dissolves, so that the adhesion of the corrosion-resistant layer of the non-etched part of the metal is reduced, which causes the corrosion-resistant coating at the junction of etching and non-etching to fall off or melt, which makes the etching pattern blurred and distorted, affecting the pattern Because of its beautiful appearance and decorative effect, the temperature should not exceed 45℃. Similarly, if the etching time is too long, especially when the temperature of the etching solution is high, the immersion time of the corrosion-resistant ink or the protective coating is too long, it will also have the aforementioned side effects and adverse consequences, so the time control should be appropriate , Can not be soaked for too long, generally should not exceed 20-25min.

(4) Examples of chemical etching pattern decoration

1. Decorative materials

Decorative metal plates: ordinary steel, stainless steel, copper and copper alloys, aluminum and aluminum alloys, etc., take the stainless steel plate as an example, and the plate thickness is 1 to 3mm.

Chemical raw materials: screen printing photosensitive glue (such as DH diazonium type produced by Zhejiang Kunshan Chemical Coating Factory), acid-resistant inks are 99-956 type and 99-200K type (products of Guangdong Shunde Daliang Ink Factory), others are commonly used chemical chemicals drug.

2. Process flow

Stainless steel plate → degreasing → washing → drying → screen printing → drying → water immersion → etching pattern leaf (sheet) washing → deinking → washing → polishing → washing → coloring → washing leaf (sheet) hardening treatment → sealing treatment → Wash the leaves (sheets) to dry → inspect → product.

3. Specific operations and precautions

(1) Degreasing Degreasing is to make the screen printing ink have a good adhesion to the plate, so the metal plate must be completely degreasing before printing. There are many degreasing methods, which can be selected according to the situation and needs. For example, conventional chemical degreasing, surfactant degreasing, or even electro-degreasing, ultrasonic degreasing, etc. can be used. Commercial special degreasing agents can also be used. After thoroughly cleaning, it is dried and then transferred to screen printing.

(2) Screen printing uses 150 mesh stainless steel, polyester or nylon monofilament nets, fixed on the screen frame with a stretcher, and then squeezes DH diazo photosensitive glue with a sizing machine, and coats it for 2 to 3 times. After the coating film is dried, attach the photographed black and white film with the pattern to the coating screen. After exposure and development, the screen printing template is prepared, and then the stainless steel plate and the pattern template are fixed on the corresponding position of the screen printing machine. , Use alkali-soluble, acid-resistant ink to print the required patterns and dry (or dry) naturally. If baking, the temperature should not be too high and the time should not be too long, otherwise the alkali solubility of the ink will decrease, and it will not be easy to clean up when the ink is removed. Under normal circumstances, dry naturally for 1 hour. Drying at 55~60℃, 4~5min.

(3) Pattern etching process The formula and process conditions of pattern chemical etching solution are as follows:

Iron chloride (FeCl3) 650~800g/L etching accelerator 85~lO0g/L

Hydrochloric acid (HCl, 38%) 85~120g/L etching solution temperature 10~45℃

Phosphoric acid (H3P04) 20~30g/L Dipping time 15~25min

Strictly control the temperature and time of the solution during operation. If the temperature is too high or the time is too long, the adhesion between the ink and the board surface will decrease, and the ink may fall off at the etched and non-etched places, resulting in blurry patterns, affecting the accuracy of the etching and the decorative effect.

(4) Ink removal after etching After etching, the protective alkali-soluble acid-resistant ink must be removed. The method is to immerse in 40~60g/L NaOH lye, the temperature is controlled at 60~70℃, soak for 3~5min, whichever is the clean ink. Then rinse the lye on the surface with water to neutrality. (5) Post-etching treatment After the etched patterned stainless steel plate has been de-inked and cleaned, the following additional decoration treatments can be made according to the different needs of users.

①For those that require the preservation of the original color and gloss of stainless steel, after removing the ink and cleaning, put it in a solution of 50% HN03 (volume fraction) and 50% H20 for 10-20 minutes for passivation treatment to make the stainless steel etching pattern board Get a new protective film, you can get decorative products.

②For those that require the preservation of the original color of stainless steel, but require higher brightness and brightness, after removing the ink and washing, electrolytic polishing is performed first, and then the surface is passivated.

The solution formula and process conditions of electrolytic polishing are as follows:

Citric acid 50%~70% solution temperature 40~60℃

Sulfuric acid 20%~l5% current density 15~30A/dm2

Water 10%~25% Polishing time 5~10min

Cathode material lead plate

③In order to improve the decoration of products, some users require to change the color of the original stainless steel. In this regard, after the stainless steel is etched and the ink on the surface is cleaned, it is electropolished and then chemically or electrolytically colored. After coloring, the colored film must be hardened and sealed to obtain the desired decorative products. The formula and process conditions of the chemical coloring solution are as follows:

Sulfuric acid (H2S04) 270~300g/L, solution temperature 65~80℃

Chromic anhydride (Cr03) 450~500g/L The processing time is from blue to orange to golden

(NH4)6Mo7024·4H2040~50g/L color-green, color changes with time

After chemical coloring, a hardening treatment (or solid film) is required to stabilize the colored film and improve the quality and wear resistance of the colored film. The solution formula and process conditions of the hardening treatment are as follows:

Potassium dichromate (K2Cr207) 10~20g/L solution temperature 65~80℃

Sodium hydroxide (NaOH) 3~5g/L treatment time 2~3min

Solution pH6.5~7.5

After the above-mentioned hardening (solid film) treatment of the colored film, the hardness, abrasion resistance and corrosion resistance have been improved, but the film layer has pores, and further sealing treatment is required. If the colored film itself is of good quality and high hardness, hardening treatment is not necessary, but sealing treatment must be performed. The composition and process conditions of the sealing solution are as follows:

Sodium silicate (Na2Si03) 10g/L solution temperature 100℃

Boiling sodium dodecylbenzene sulfonate 2~5g/L, treatment time 4~6m

In addition to chemical coloring, electrolytic coloring can also be used. The formula and process conditions of the electrolytic coloring solution are as follows:

Chromic anhydride (Cr03) 80~260g/L Current density 0.05~0.10A/dm2

Sulfuric acid (H2S04) 25% (volume fraction) Coloring time l0~30min

Solution temperature 70~90℃

In the coloring process of this coloring solution, the process conditions have a greater impact on the color. The first is the effect of the concentration ratio of sulfuric acid to chromic anhydride on the color. When the concentration of chromic anhydride is high, it is golden yellow, and when the concentration is high, it becomes purple-red. The effect of temperature on coloring is: as the temperature increases, the color gradually deepens. The effect of the coloring time is: the coloring starts at 5 minutes, and the color deepens with the increase of time, and the color is basically stable after 20 minutes. The effect of current density on coloring is: at 0.03A/dm2, it is rose, and at 0.05A/din2, it is 18K gold.

Hardening treatment is also required after electrolytic coloring. The hardening treatment can be done by chemical methods (for example, above) or electrolytic method. The solution formula and process conditions of the electrolytic hardening treatment are as follows:

Chromic anhydride (Cr03) 240~280g/L Cathode current density 0.2~1.0A/dm2

Sulfuric acid (H2S04) 2~3g/L anode material lead or lead-antimony alloy

Solution temperature 50~55℃ Treatment time 10~15min

After the hardening treatment, it should also be sealed, boiled in a boiling sodium silicate solution for 5 minutes, taken out for cleaning, and dried to obtain decorative boards with various colors and luster.

Informatization injects vitality into metallurgical automation

In recent years, the external competition environment faced by steel companies has undergone earth-shaking changes. In terms of energy consumption, the iron and steel industry consumes about 11% of my country’s total energy consumption. Compared with the world’s advanced level, the energy consumption per ton of steel is 10% higher. In terms of customer service, customers are increasingly demanding steel varieties and specifications. The more diversified, the more stringent requirements on product quality and delivery time. In addition, the financial crisis has added many variables to the development of the domestic metallurgical industry, and the development of metallurgical enterprises can be described as “internal and external troubles.”
Relevant policies recently issued by the state show that the development of informatization of steel enterprises has been highly valued by Chinese government departments and metallurgical enterprises. Under such circumstances, some large domestic steel and metallurgical enterprises have begun to consider implementing advanced production and operation management models and systems to adapt to changes in the external competitive environment.

The demand of iron and steel enterprises drives the development of automation technology

Before the 1970s, my country’s iron and steel enterprises generally adopted single-loop control, and the control equipment was conventional instruments with simple control levels. Since the 1990s, the automation of my country’s metallurgical industry has developed rapidly. Under the requirements of process optimization and informatization, the control equipment is mainly PLC, DCS, FCS, etc., and the control level has reached the level of quasi-unmanned. In recent years, some large-scale steel enterprises in my country have basically realized the informationization of the whole plant, and the three-level structure of BPS/MES/PCS has appeared in the control system. Liu Wei, deputy director of the Zhongkuan Cold Belt Plant of Lingyuan Iron and Steel Company, said that the first world trade war of China’s entry into the WTO broke out in the iron and steel industry. Coupled with the impact of the financial crisis and the shrinking of the international market, iron and steel enterprises have to be tested. Higher than other industries. In such an open environment, the improvement of the automation level of domestic steel plants is also the general trend.

At present, in addition to producing various types of automation products and equipment, domestic and foreign electrical automation companies have integrated equipment that has become the first choice of steel companies. It is understood that while Siemens, ABB, Schneider, GE and other companies provide products, they will also provide individualized solutions for metallurgical enterprises. Factory Director Liu said: “Automation instruments, sensors, electronic control devices and technologies, including intelligent control automation systems all have a lot of room for development.”

It is understood that basic automation in the metallurgical industry is the most basic part of the production process. The more complex the production process, the higher the degree of basic automation. In the blast furnace system, it even reaches 100%, and continuous casting and rolling steel also reach nearly 99%; production Process control automation technology has also been significantly improved. Production process control automation is an important link to improve product quality and ensure optimal control of the production process. A large number of mathematical models and artificial intelligence technologies are widely used at this level; workshop management level or manufacturing execution The system has received widespread attention from iron and steel companies in recent years. Some domestic companies have introduced advanced technologies at home and abroad to develop production execution systems on new or renovated production lines. Factory Manager Liu explained: “The manufacturing execution system is mainly composed of the regional management computer system to complete many functions such as online operation planning, production scheduling management, and quality tracking control.”

Speed ​​up the promotion of informatization

The position of the workshop management level or the manufacturing execution system in the enterprise information architecture is very important. Through the seamless connection and system integration of the control system and the management information system, the real-time production data and instructions can be communicated smoothly. Director Liu introduced to reporters: “As of 2008, enterprises that account for 50% of the national steel output have achieved informatization. However, there are still some iron and steel plants that have a low level of informatization applications. These plants have only built computer local area networks in the workshops. And a small amount of production report processing, and a large amount of actual production data still needs to be completed manually.”

He also proposed that the promotion of informatization should take into account the factors of the steel company’s automation level. For companies that already have a complete set of automated production lines, they have accumulated a lot of useful experience in informatization, so the focus of their work is on the innovation of business processes and systems; companies with a high level of equipment automation can shift their focus to corporate management For iron and steel enterprises with long equipment age, serious aging, low level of automation, and weak funds, it is very difficult to implement large-scale information systems, so we should strengthen the equipment basic automation and introduce some simple computer aids in business management. system.

At present, my country’s leading steel companies have listed informatization as one of the measures to improve their core competitiveness. With the development of information technology, the application of MES has become the focus of attention of steel companies. With the further acceleration of product structure adjustment, the demand for MES will become more and more urgent. The state has taken active and encouraging measures in the development of enterprise informatization, which has also greatly promoted the informatization construction process of steel enterprises.

Overview of metallurgical automation trends

In the development of detection technology and instrumentation, the trend of networking, virtualization, intelligence, and high precision is becoming more and more obvious; in industrial control, the application of PLC and DCS is mainly used, and the application prospect of fieldbus technology is promising. Director Liu introduced that in the metallurgical industry, PLC and DCS have a tendency to move closer to each other. That is to say, PLC has strengthened the loop control function, and DCS has also been greatly improved in terms of sequence control function. Regarding the choice between the two, major steel companies have different opinions. Due to price considerations, some companies prefer to choose a full PLC system.

At present, the development of visualization technology and monitoring system also provides more convenience for the metallurgical industry. Due to the closed nature of the blast furnace, the importance of instrument detection is particularly important. In recent years, due to the development of testing technology, computing technology, image processing technology, and modeling, multimedia virtual technology has made the originally vague process more transparent and visual, which greatly facilitates the actual operation of steel employees. In addition, in order to reduce costs, foreign countries have introduced the concept of “unmanned factory” or “quasi-unmanned factory” into the metallurgical industry. The unmanned operation of the entire workshop allows the steel company’s staff to save the most.

Finally, Director Liu added: “Due to different industries, the corresponding automation products or technologies are quite different. The metallurgical industry contains the characteristics of the traditional automation industry, but also includes the automation technology applied in the power field of power plants, such as The development of advanced clean coal combustion technologies such as coal gasification combined cycle, atmospheric circulating fluidized bed boilers and pressurized fluidized bed combustion boilers in the metallurgical industry is relatively optimistic. As the main body of the metallurgical industry, I personally think that the development of fieldbus technology The application space is large.

Application of Easy Control Configuration Software in Baosteel’s Flame Cutting Production Line for Wide and Heavy Plate

Steel connectors are used for metal parts connecting steel components, wood components, and steel and wood components. Steel connectors mainly include rivets, bolts, high-strength bolts, welding rods, pivots (pins) and various nails.
Rivet   refers to a cylindrical short rod with a semi-circular nail head at one end. It is inserted into each steel plate or section steel nail hole to be connected, and the protruding end is pressed or hammered into a second nail head. According to the shape of the rivet, it is divided into four types: semi-round head, high head, countersunk head, and half countersunk head. Round head rivets are commonly used in bridges and building structures. The rivets are made of rivets No. 2 steel (ML2) and rivets No. 3 steel (ML3) with better plasticity. The rivet connection has been gradually replaced by welding and high-strength bolts due to the labor-consuming, material-consuming, complicated riveting process, and easy loosening under dynamic loads.

Bolt   is usually a cylindrical metal rod with a square or hexagonal head at one end and a thread at the other end, equipped with nuts and washers, which can fasten steel or steel-wood components together. The material is No. 3 steel or riveted No. 3 steel, which can be divided into two types: rough and refined bolts. The manufacture and installation requirements of refined bolts are relatively high, and they are rarely used at present. The surface of rough bolts does not require special processing, and is mainly used for tension connection and installation connection.

High-strength bolts  Using high-quality carbon structural steel or alloy structural steel, a special bolt with higher strength and a certain degree of plasticity and toughness obtained through heat treatment. A strong pre-tension must be applied during use. At present, there are two types of large hexagon head and torsion shear type in China. The commonly used models in civil engineering are M16, M20, M22, and M24. The maximum specifications can reach M30, and the performance level is divided into 10.9S and 8.8S. The materials are mainly 20MnTiB steel, 40B steel, 35VB steel, 45# steel and 35# steel. High-strength bolts are used for the connection of steel structures in industrial and civil buildings, highway and railway bridges, tower mast structures, pipeline supports, hoisting machinery, etc.

Welding Rod  A rod-shaped metal strip that melts and fills the joints of welded parts during electric welding. It is coated with anti-oxidation (alloying, etc.) flux. According to the mechanical properties and chemical composition of the metal material to be welded, as well as the welding seam requirements and equipment process conditions, choose different types and models of electrodes. Commonly used structural steel electrodes are divided into four categories according to the deposited metal mechanical properties, welding power source, use and welding conditions: T42-0~T42-7; T50-0~T50-7; T55-X; T60-X. Electrode coatings are divided into titanium oxide type, titanium calcium oxide type, ilmenite type, iron oxide type, cellulose type, low hydrogen type and so on. Welding has been widely used in the production and installation of steel structures such as industrial and civil buildings, bridges, tower mast structures, and container equipment.

Pivot  , also known as a pin, is a metal cylindrical connector used to connect two members that can rotate freely at the joint without pretensioning. One joint only needs one pivot, so the diameter is larger. Generally used on steel structures such as crane booms, arch hinges, and disassembly bridges.

Features of heat treatment and surface modification technology

The performance of the material does not depend solely on the type and composition of the material. Changing the internal structure of the material through heat treatment and surface modification will greatly change the material performance. For example, the hardness of high-speed steel in the annealed state is not higher than 280HB and has quite good plasticity and toughness. After quenching and tempering, it has high hardness, red hardness and wear resistance. Since the content of alloying elements dissolved in the matrix and the grain size of austenite are related to the quenching temperature, the trend is that the hardness and red hardness increase with the increase of the quenching temperature, the toughness decreases, and the strength increases first. Descending (Figure 1). Using this rule, the best quenching temperature can be selected according to the use characteristics of different tools and molds (Table 1). The blades and handles of the turning tools are relatively thick, and the strength requirements are not high, and the impact load is lighter. The quenching temperature close to the melting point can be used to dissolve as much alloying elements and carbon as possible into the austenite, thereby improving the red hardness and wear resistance. The cutting edge of the drill bit is not easy to cool when drilling. It is hoped to increase its red hardness as much as possible. However, in order to prevent twisting, the drill bit needs to have higher strength, so its quenching temperature is slightly lower than that of the turning tool. The cutting edges of milling cutters and reamers are relatively thin. In order to avoid chipping, sufficient toughness is required. The quenching temperature should be appropriately lowered. The main damage method of small drills is twisting or breaking. In order to ensure higher strength, the quenching should be further reduced. Heating temperature. The cold extrusion die is subject to high stress, but does not require high red hardness, so select the quenching heating temperature that appears the peak strength, and for some slender or complex shape, subject to greater impact load, you should choose Lower quenching temperature. Table 1 shows that for tools or molds made of the same kind of steel, different quenching temperatures should be selected according to use conditions and failure modes, and the range of changes reaches 150°C. But for a specific workpiece, only ±5°C deviation is allowed.

Structural steel and low-alloy tool steel have a similar situation. The pre-heat treatment structure, quenching heating temperature, cooling method, and tempering temperature all have a significant impact on the performance of the steel. The different combinations between them can make the material obtain different comprehensive properties. . The strength, hardness, toughness, plasticity and elastic limit of structural steel all change with the tempering temperature after quenching. For workpieces that require high plasticity, high toughness, especially low notch sensitivity, high temperature tempering (tempering and tempering) Treatment), and the workpieces that require high strength and higher hardness should be tempered at about 200 ℃, such as 30CrMnSi, 40CrNiMo after quenching at 200 ℃, the tensile strength can be as high as 1600″1800MPa, which is about 1 times higher than quenching and tempering. Springs and other elastic components are usually tempered at medium temperature showing the peak of elastic limit. In addition, processes such as austempering, two-phase zone heating quenching and deformation heat treatment can make structural steel good strength and toughness. As for various chemical heat treatment and surface coating technologies The concentration and depth of the carburized layer surface and the control of the concentration gradient and performance gradient can be adjusted by adjusting the process parameters to adapt to the requirements of different service conditions on the overall performance of the workpiece. For example, the carburizing treatment of different parts should be There are different technical requirements to obtain good performance (Table 2). For oil drilling roller cones, the surface concentration of the carburized layer is reduced from 0.9″1.0%C to 0.7″0.8%C, and the concentration distribution curve is flat. , The service life is increased from 27 hours to 52 hours, and the effect that one drilling team can reach two drilling pairs is received. For example, the surface modification treatment by ion implantation can greatly improve the overall strength and toughness. Improve wear resistance, reduce friction coefficient, improve corrosion resistance, apply to bearings and various friction parts in various transmission mechanisms on spacecraft, wear parts in hydraulic motors on aircraft, and sleeves for mud pumps in the petroleum industry Good results have been achieved in cylinders, etc. In some cases, some seemingly “informal” heat treatment processes are used for the characteristics of the workpiece, and surprising results can be obtained: the quenching temperature range of 3Cr2W8 hot mold steel is generally 1050″1120℃, but The boiler steel pipe hot extrusion die, which is equivalent to the two sides of the steel pipe radiating ribs in the die cavity, bears great stress and is easy to yield in the hot state and cause the die to fail. After the experiment, the quenching temperature is increased to 1170″1180℃, and the water is cooled to “650℃ during quenching cooling, and then transferred to a low-temperature salt bath for cooling. The mold life is increased several times; the blade of the rice harvester is treated with high-concentration carbonitriding; A large amount of carbides and retained austenite appear on the surface layer, which is regarded as unqualified according to conventional inspection standards. However, due to its high wear resistance and good corrosion resistance, the service life of rice harvester blades is longer than that of conventional carburizing Deal with several times higher.

A cursory review of the above-mentioned facts that have long been well-known is just to illustrate an easily overlooked view: the optimal heat treatment process cannot be the same, and the properties of the same material will change due to the heat treatment method and process parameters. , And various performance indicators often fluctuate one after another. Only by selecting appropriate heat treatment process parameters and obtaining the best comprehensive performance compatible with the use status and failure modes of the workpiece can high-quality products be manufactured. This is the characteristic, difficulty and charm of heat treatment and surface modification technology. , Full of space and leeway for people to exert their subjective initiative.

History has proved that improving heat treatment technology and making full use of the potential of materials are often catalysts for product upgrading. After quenching and tempering, the yield strength after high temperature tempering after quenching is about 600” 900 MPa. Both the strength and toughness are significantly better than normalizing treatment, so it became a common heat treatment process for structural steel. Before the Second World War Researchers in the Soviet Union found that after 30CrMnSi quenching and low-temperature tempering, or austempering, the yield strength reaches 1500 MPa and maintains sufficient toughness. It is used to manufacture aircraft landing gear. Medium and low-carbon structural steel quenching and low-temperature tempering treatment is also used Military products such as bullet-proof shields of artillery, and subsequent development of a series of “ultra-high-strength steels” characterized by quenching and low-temperature tempering treatments promoted the upgrading of many important products, such as the rotor of the hydraulic coupler of high-power gas turbines , It transmits tens of thousands to hundreds of thousands of kilowatts of power, and the speed is more than 20,000 revolutions per minute. The original design is SEA4340 steel quenching and tempering treatment, and the yield strength is 800MPa. Later, quenching and low temperature tempering are used to achieve a yield strength of 1800MPa. The weight of the entire coupling is reduced to 1/4 of the original. This is very beneficial for improving the performance of the ship.

Surface modification technology also plays an important role in the development of high-end products. As we all know, the thermal efficiency of gas increases with the increase of gas temperature, but the heat-resistant temperature of superalloys limits the increase in combustion chamber temperature. In foreign countries, due to the successful deposition of a composite coating containing honeycomb ZrO2 on the surface of the heat-resistant alloy, it plays a role of heat insulation, making the temperature of the heat-resistant alloy blades more than 150 ℃ lower than the gas temperature, and developed a higher combustion chamber temperature Gas turbines promote the upgrading of aero engines.

Even in the general machinery manufacturing industry, the technological progress of heat treatment and surface modification is also of great significance to product innovation. For example, the productivity of the cold heading machine for producing standard parts has now reached 600 pieces/min, compared to more than two decades The first 60 pieces/min is increased by 10 times. The outlook of the standard parts industry has been greatly changed. In fact, the cold heading machine is not complicated. It is not difficult to design and manufacture the 600 pieces/min cold heading machine. The problem is that the small hexagonal punch has a lifespan of less than 20,000 pieces. In this case, increase The speed of the cold heading machine is meaningless. Because standard parts are products with extremely large batches, it is usually required that the life of each punch must exceed one shift, otherwise it is difficult to carry out production management. In the early 1980s, through the improvement of the heat treatment process, the life of the punch was increased to more than 50,000 pieces, and the cold heading machine with 100 pieces/min was available. And in the 1990s, the hexagonal punch was made by vapor deposition of titanium nitride. Surface modification treatment has increased its life to more than 350,000 pieces. Become a catalyst for high-speed cold heading machines.

The thin-walled ring gear of a special gearbox is characterized by its ability to significantly reduce the volume and weight of the gearbox, but it is difficult to manufacture with conventional gear heat treatment methods. It is difficult to control carburizing quenching or induction heating quenching. Heat treatment distortion, while the conventional nitriding treatment can not meet the requirements of the contact fatigue strength of the gear, only the application of dynamic controllable nitriding process increases the contact fatigue strength from 1400 MPa to 1700 MPa, and the research has successfully controlled the nitriding distortion of the thin-walled ring gear The method that made the trial production of special gearboxes succeeded.

Only from these examples can be reflected: the technological progress of heat treatment has an important role in promoting product innovation.

In view of the above characteristics, in order to improve the technical level of heat treatment, a systematic study of the influence of heat treatment process parameters on the structure and properties of materials should be carried out first, and secondly, the research work should not only stop at the level of sample research. The heat treatment process research needs to be combined with the product bench test, installation test and failure analysis. After continuous exploration and improvement, the effect of greatly improving the life can be achieved. For example, the cold extrusion punch of truck piston pin shown in Figure 3. To withstand a unit pressure of about 2000MPa, it needs to have a high compressive yield strength, and its shape is slender and easy to break, and it requires sufficient toughness. The extruded metal strongly rubs against the ligament during the extrusion process, so it needs high resistance Abrasion and certain thermal stability. It is made of W6Mo5Cr4V2 high-speed steel. At first, the standard heat treatment specifications given in the manual were used for treatment, and the service life was less than 400 pieces. The failure mode is that the punch breaks during pressing. In order to improve the toughness of the material, the quenching temperature was reduced from 1225°C to 1190°C, which received significant results and the service life was increased to about 2500 pieces. Although the toughness can be further improved by further reducing the quenching temperature, the service life will fall. After careful analysis of the working conditions and failure modes of the punch, it is found that the cutting edge of the punch that is heated and quenched in the low temperature range is gradually drawn, and the resistance during demolding becomes larger and larger. During the demolding process, due to impact tensile stress The effect of causing fracture. For this specific situation, quenching at 1190°C and tempering at 560°C for 4 times, and then gas nitrocarburizing treatment. The hardness of the surface layer (about 0.02mm) is increased to more than 1000HV, while the overall strength and toughness are maintained, and the service life is increased to more than 10,000 pieces.

Furthermore, considering that the heat treatment process parameters are very sensitive to the effect of material properties, in order to ensure the reproducibility and consistency of quality, it is necessary to research and develop advanced heat treatment process equipment, precise and reliable heat treatment process control technology, reasonable design fixtures, and regulations. And strictly implement reasonable furnace installation and operation methods. So improving the quality of heat treatment and its reproducibility is a systematic project. It is not surprising that there are large gaps between different countries and different companies in this field.

Improve the heat treatment process, reduce the heat treatment deformation of the mold

The deformation of the mold after quenching, no matter what method is adopted, the deformation is unavoidable, but the following methods can be used to control the precision and complex molds that must strictly control the deformation amount.

1. Using quenching and tempering heat treatment

For precision and complex molds with low basic hardness requirements but high surface hardness requirements, quenching and tempering heat treatment can be performed after rough machining of the mold, and low temperature nitriding treatment (500″550ºC) after finishing. Due to the low mold nitriding temperature, There is no phase transformation of the matrix structure. In addition, the furnace is cooled to room temperature, and the cooling stress is less, and the mold deformation is small.

2. Using pre-heat treatment

For precision and complex molds, if the hardness requirements are not too high, pre-heated pre-hardened steel can be used, and the die steel (such as 3Cr2Mo, 3CrMnNiMo steel) can be pre-heated to reach the hardness in use (lower hardness is 25″35HRC , The higher hardness is 40″50HRC), and then the mold is processed and formed without heat treatment, so as to ensure the accuracy of the precision and complex mold.

3. Use age hardening die steel

Aging hardening steel can be used for precision and complex molds. For example, PMS (1Ni3Mn2CuA1.Mo) steel is a new type of aging mold steel. The hardness after solution quenching at 870ºC is about 30HRC, which is convenient for machining. After the mold is formed, it can be processed at about 500ºC. The high hardness of 40″45HRC can be obtained by the aging heat treatment, and the mold deformation is small, and only needs to be polished. It is an ideal steel for precision and complex molds.

The influence of heat treatment heating process

1. The influence of heating speed

The deformation of the mold after heat treatment is generally considered to be caused by cooling, which is incorrect. For molds, especially complex molds, the correctness of the processing technology often has a greater impact on the deformation of the mold. A comparison of some mold heating processes can clearly show that the heating speed is faster and often large deformations.

(1) Causes of deformation Any metal will expand when heated. Because steel is heated, the uneven temperature of each part (that is, uneven heating) in the same mold will inevitably cause inconsistent expansion of each part in the mold The formation of internal stress due to uneven heating. At the temperature below the transformation point of steel, uneven heating mainly produces thermal stress. If the heating exceeds the transformation temperature, uneven heating will also produce unequal time of the transformation of the structure, which will result in structure stress. Therefore, the faster the heating rate, the greater the temperature difference between the mold surface and the core, the greater the stress, and the greater the deformation of the mold after heat treatment.

(2) Preventive measures The complicated mold should be heated slowly when heating below the phase transition point. Generally speaking, the deformation of the mold in vacuum heat treatment is much smaller than that in the salt bath furnace. ‚Using preheating, for low-alloy steel molds, one preheating (550-620ºC); for high-alloy steel molds, two preheating (550-620ºC and 800-850ºC).

2. The influence of heating temperature

In order to ensure that the mold reaches a higher hardness, some manufacturers believe that it is necessary to increase the quenching heating temperature. However, production practice shows that this approach is inappropriate. For complex molds, heating and quenching are also performed at the normal heating temperature. The heat treatment deformation after heating at the allowable upper limit temperature is greater than the heat treatment deformation heated at the allowable lower limit temperature. Much larger.

(1) The cause of deformation It is well known that the higher the quenching heating temperature, the more the grains of steel will grow. As larger grains can increase the hardenability, the greater the stress generated during quenching and cooling. Furthermore, since complex molds are mostly made of medium and high alloy steel, if the quenching temperature is high, the amount of retained austenite in the structure will increase due to the low Ms point, which will increase the deformation of the mold after heat treatment.

(2) Preventive measures In the case of ensuring the technical conditions of the mold, the heating temperature should be selected reasonably, and the lower limit quenching heating temperature should be selected as far as possible to reduce the stress during cooling, thereby reducing the complicated heat treatment deformation.

Preventive Measures for Crack Defects of High Speed Tool Steel

High-speed tool steel is a high-end…
High-speed tool steel is a high-end tool steel with good wear resistance and toughness. However, if you do not pay attention to it in production, defects such as cracks will easily occur, resulting in scrap. This is mainly because:

1. Low plasticity. High-speed steel has many alloying elements, especially S, Ph, Sn and other impurity elements, which tend to weaken the inter-grain bonding force and reduce the plasticity.

2. Large deformation resistance. The alloy composition of high-speed steel is complex, the recrystallization speed is slow, the temperature is high, and it has high deformation resistance at the deformation temperature.

This article is provided by Machinery Knowledge Network, please pay attention to the content provided by Machinery Knowledge Network

3. Narrow forging temperature range. High-speed steel heating temperature is too high, it is easy to overheat, over-burn, stop forging temperature is too low, it will produce coarse-grain phenomenon, theoretically high-speed steel forging temperature range is very narrow, generally 200-280 ℃.

4. Poor thermal conductivity. The thermal conductivity of high-speed steel is much lower than that of carbon steel. It needs to be heated slowly at 600-900℃, otherwise it will cause temperature stress and cause metal brittleness.

The relevant preventive measures are:

1. Strictly control the metal content of high-speed steel raw materials. For example, the tin content must be strictly controlled below 0.08%.

2. It is stipulated that the ingot must be peeled or cleaned by the grinding wheel before heating forging to improve the performance of high-speed steel processing.

3. Control the heating temperature, holding time and deformation temperature of high-speed steel, and adopt multi-fire forging.

4. When the slab is drawn, lightly tap it at the beginning, and increase the amount of deformation after the as-cast structure is properly broken and the plasticity is improved. When free forging is long, the deformation of each fire is controlled within 2-4 times, and it should be sent from the head to the tail.

This article is provided by Machinery Knowledge Network, please pay attention to the content provided by Machinery Knowledge Network

5. When forging high-speed steel, reduce the number of continuous rotation deformations in the same part of the raw material, and specify less than 8 times.

Ultra-pure spring steel wire

Recent studies have shown that the main factors affecting the fatigue life and reliability of oil-quenched-tempered steel wire for valves are the form and content of inclusions in steel: large particles do not deform Type D inclusions and Type B inclusions lead to a sharp decrease in the fatigue life of the spring, while phosphorus, The high content of sulfur, arsenic, lead, tin, and antimony will also increase the temper brittleness of steel. Ultimately reduce the fatigue life. For this reason, ultra-pure oil quenched-tempered steel wire was developed.

The so-called ultra-pure steel is refined outside the furnace, vacuum degassed, electroslag remelting, composite slag system, inclusion deformation treatment, electromagnetic stirring and other technical means to minimize the gas (oxygen, nitrogen, hydrogen) in the steel. The content of non-metallic elements (phosphorus, sulfur, arsenic) and low melting point metals (lead, tin, antimony) can transform large non-deformable inclusions into plastic or semi-plastic fine inclusions. At present, 55CrSiA ultra-pure steel developed in Japan and Europe The 67CrVA. ultra-pure steel developed has made remarkable achievements.

 

The cause of elastic yellow fracture under low stress is non-metallic inclusions, and the cause of fracture under high stress is often surface defects. Therefore, it is necessary to strengthen the grinding and cleaning of the billet used for rolling wire rod, and strengthen the research on the control of cooling and rolling of the wire rod. Or stripping or grinding the wire surface. Clear defects such as surface decarburization, cracks, and folding. At present, among the oil-quenched steel wire production enterprises in China, only Shanghai Steel No. 2 Plant has stripping equipment, while other manufacturers have no secondary equipment. This is also an important factor restricting the improvement of the quality of oil quenched steel wire products in my country. The intermediate annealed structure of the wire rod or semi-finished product should be fine flake pearlite to meet the requirements of rapid heating for oil quenching. Some materials suggest that the intermediate heat treatment of 67CrVA. adopts lead quenching treatment to prepare for oil quenching heating.

What is the method of stainless steel golden process

The method of stainless steel golden process:
Stainless steel products are golden: the surface of stainless steel is treated in chromic acid and sulfate solution to give a golden appearance. The process is as follows:

Chromic anhydride 250g/L

Sulfuric acid 490g/L

Temperature 70℃

Time 18min

The ratio and temperature of chromic acid and sulfuric acid in the above-mentioned solution can be adjusted according to the required color. Generally, 15min can be treated for blue; 18min can be golden; 20min can be purple; 22min can be green. The color brightness of the obtained stainless steel colored film is related to the pretreatment, and the mechanical polishing effect is generally better. The coloring treatment time and temperature can be adjusted according to the specific situation. If the solution temperature cannot be increased, the treatment time can be extended to achieve the same effect.